Refrigerating control apparatus



Dec. 19, 1950 L. B. KOONTZ 2,534,455

REFRIGERATING CONTROL APPARATUS Filed June 8, 1944 I5 Sheets-Sheet 1Iiiwentor LHNO/VT 3. KOO/V72 attorney Deg. 19, 1950 L. B.IKOONTZ2,534,455

REFRIGERATING CONTROL APPARATUS Filed June 8, 1944 3 Sheets$heet 2Gttorneg Dec. 19 1950 Filed June 8, 1944 L. B. KOONTZ REFRIGERATINGCONTROL APPARATUS 3 Sheets-Sheet 3 Z'mneutor L/INONT B. IIOONTZ attorneyPatented Dec. 19, 190

REFRIGERATIN G CONTROL APPARATUS Lamont B. Koontz, Minneapolis, Minn.,assignor to Minneapolis-Honeywell Regulator Company, Minneapolis, Minn.,a corporation of Delaware Application June 8, 1944, Serial No. 539,235

19 Claims. (Ci. 62-4) The present invention relates to improved meansfor controlling the flow of refrigerant through an evaporator.

The control of flow through a refrigerating evaporator involvesdifficulties which have not, in the past, been entirely overcome.Normally, an expansion valve is used to control said flow, said valvebeing operated in response to evaporator pressure, or to refrigerantpressure and temperature at the evaporator outlet. These systems areonly partially satisfactory, especially when operated over a wide rangeof conditions.

In the present invention, applicant gains superior control over hisexpansion valve by operating same in response to either the temperatureor the heat absorbing abilities of the flowing refrigerant at two spacedlocations'within or associated with said evaporator. One of the markedcharacteristics of refrigerant flow through the evaporator is itsconstantly changing quality, that is, the constantly increasingpercentage of the refrigerant which is in the gaseous state. 01 theliquid refrigerant supplied the expansion valve, 9. portion of sameevaporates immediately on passingv through'the valve and serves toreduce the temperature of the remaining refrigerant. As the refrigerantthen flows through, the evaporator, it absorbs heat from the mediumbeing cooled, absorption of heat resulting in more of the refrigerantbeing vaporized. So long as some of the refrigerant flowing in theevaporator is liquid, and the evaporator surface is kept wet thereby,the rate of heat transfer is high,.but

when all of the refrigerant is vaporized, the rate of heat transfer islow. The considerable difference in heat transfer rate and heatabsorbing ability which exists between gaseous refrigerant and mixturesof gaseous and liquid refrigerant is used in the present system in amanner to be described.

Obviously, maximum evaporator capacity is obtained when a maximumportion of the evaporator surface is wetted by the refrigerant. However,to protect the compressor, it is essential that only gaseous refrigerantleave the evaporator. With the ordinary thermostatic expansion valve,this is insured by permitting the temperature of the refrigerant, beforeleaving the evaporator, to rise several degrees above its vaporizingtemperature, thus "superheating" same. The superheat used may be likenedto a factor of safety, for the more superheat used, the more assurancethere is that liquid refrigerant will not reach the compressor,althoughthe less eflective the evaporator will be for cooling because ofthe es amplifying means.

greater portion of same used for heating vaporized refrigerant.

It is thus an object of this invention to provide a control means whichresponds quickly and accurately to refrigerant conditions within theevaporator and operates to control the flow through said evaporator in amanner to insure full capacity operation of said evaporator and yetinsure the passage of only gaseous refrigerant to the compressor.

It is also an object to provide refrigeration control means which isadaptable for use with any conventional refrigerant, and which is ofsuchvwith other control apparatus. Additionally, the

control circuits provided are such that supplementary control factorsmay be added to the control system at will, thereby increasing theusefulness and desirability of the present apparatus.

It isan additional object to provide improved and effective means forcontrolling the flow of refrigerant through an evaporator in response tothe percentage of liquid refrigerant flowing past a predeterminedlocation in said evaporator in a manner to maintain said percentage at amaximum value consistent with safe operation of the system.

These and other objects will become apparent upon a study of thefollowing specification and drawings wherein:

Figure 1 shows a schematic embodiment of the present apparatus includingspaced temperature responsive resistance means, each of said meansincluding heater means. v

Figure 2 is a cross section of one of the present control devicesincluding a temperature responsive means and heater means, taken onthe-line 2- -2 of Figure 1.

Figure 3 is a horizontal section taken on the 7 line 3-3 of Figure 2 ofsaid device.

Figure 4 shows a modified schematic embodiment of the present inventionincorporating Figure shows a further modifled schematic embodiment ofthe present system incorporating fluid filled temperature responsivedevices.

As suggested in the objects and as noted in the figures, the presentinvention includes control means for operating a more or lessconventional expansion valve in a conventional compressor typerefrigeration system. The control means used responds to conditions ofthe refrigerant at two spaced locations within, or closely associatedwith, the evaporator. The refrigerant flow is modified by said controlmeans to maintain the condition differential constant between saidspaced locations.

To disclose the present control means, a preferred form of same isdisclosed in Figures 1, 2. and 3, this form incorporating heatedtemperature responsive resistors for the primary control elements.Figure 4 is a modification of the preferred form wherein supplementaryheat is not supplied to the thermally sensitive resistors, and Figure 5shows another modification wherein heat is supplied to fluid filledtemperature responsive means which comprise the primary control elementsin this modification. A detailed description of the above mentionedforms or modifications of the present invention follows:

Figure 1 In Figure 1, there is schematically shown a quite conventionalcompressor operated refrigeration system. Compressor I0, driven by anelectric motor ll, discharges through pipe l2 into a combined condenserand receiver [3, wherein the compressed refrigerant is condensed andliquified in the usual manner. Condenser I3 supplies liquid refrigerantthrough pipe I4 and expansion valve l5 to evaporator l6. Expansion valveI5 is a conventional motor operated valve, it being driven by motor 2|,as shown. The outlet of evaporator I6 connects to suction pipe H, whichis connected to the inlet of compressor I0. Preferably, a safety trap 38is included in suction pipe H to positively prevent liquid refrigerantfrom entering the compressor.

The operation of compressor motor H is controlled by relay l 8, which inturn is controlled by a manual switch I9, controller 20, and floatswitch 45 of safety trap 38. Relay l8 comprises a coil 44 and twoswitching means. One switching means, which controls the operation ofmotor ll, comprises switch arm 40 and fixed contact 4|. Arm 40 moves outof engagement when coil 44 is deenergized. The second switching means,which controls a shunt associated with the control circuit of motor 2|,comprises switch arm 42 and fixed contact 43. Arm 42 breaks engagementwith 43 .when coil 44 is energized. Controller 2|! may be of anyconventional sort, but preferably it is one responding to suctionpressure, head pressure and, if desired, box temperature, such asdisclosed in the copending application of Carl G. Kronmiller, Serial No.371,001, filed December 20, 1940, now Patent No. 2,377,503, is-- suedJune 5, 1945. Safety trap 38 comprises a receptacle which is adapted toreceive any liquid refrigerant which may flow through pipe I! toward thecompressor. If sufiicient liquid accumulates in 38 to raise float 39,the contacts of float switch 45 are opened. Pipe 41 including valve 48is provided to return any oil that may collect in said trap to thecompressor.

With float switch 45 closed and the switching means of controller 20closed, closing manual motor ll. Motor II will then start and run untilit is stopped by opening manual switch l9, by conditions causing openingof the switch means of controller 20, or by the accumulation of liquidrefrigerant in safety trap 38 causing opening of float switch 45.Normally, once the compressor is started by manual switch l9, it will beautomatically controlled thereafter by controller 20 in a manner whichwill be made clear upon in spection of the aforementioned copending ap--plication.

It was previously noted that expansion valve I5 is operated by motor 2|.Motor 2| is a standard modulating motor such as widely used in thecontrol art, and comprises a reversible electric motor driving through agear train, a balanced armature type relay, and a follow-up resistancealso driven by said gear train. For a more complete disclosure of amotor such as 2|, reference is made to Patent 2,028,110, issued to D. G.Taylor. In said patent, and in the present disclosure, it will be notedthat the operation of motor 2| depends on its supply of current and alsoon the conditions of balance of an electrical network. Motor 2| issupplied current by the circuit: line 50, wire 5|, wire 67, motor 2|,wire 68, wire 55, and line 51.

It was previously noted that expansion valve l5 controls the fiow ofrefrigerant in the present system and that motor 2| controls theoperation of said expansion valve. It thus appears that the heart of thecontrol means of the present system is the means controlling theoperation of motor 2|.

The control circuit for the system of Figure 1 is seen to comprise anelectrical network having a source of current and two branches. Currentis supplied by line 51 through wire 10 to the center control terminal ofmotor 2|, and by line 50 through wire 14 to the left and right controlbranches. The left control branch comprises wire 1|, attached to theleft control terminal of motor 2|, box temperature control device 30,wire [2, temperature responsive resistor 25 of control device 23', andwire 13 which completes the left branch of the control circuit andconnects to wire 14. The right control branch comprises wire 11 attachedat one end to the right hand control terminal of motor 2|, resistor 22,wire 16, temperature responsive resistor 25 of control device 23, andwire 15 which attaches to wire 14 and completes the right hand controlbranch of motor 2|. It will be noted that devices 23, 23' and 30 are thecontrol elements, or condition responsive impedance means, in thecircuit and, neglecting device 30 for the moment, the division ofcurrent flow through the two branches will depend on the relativeresistances of resistors 25 and 25'.

To improve the response of resistors 25 and 25' to the conditions of theflowing refrigerant, in a manner that will be more fully explainedlater, heater resistors 26 and 26' are provided for control devices 23and 23', respectively. These heater resistors are energized andcontrolled by the following circuit: Line 50, wire 80, resistor 25, wire8|, resistor 26', wire 82, rheostat 83, wire 84, and line 51. Rheostat83 controls the heating effects of resistors 26 and 26', and thus theheating of devices 23 and 23'.

By heating devices 23 and 23', resistors 25 and 25' each respond to atemperature which is the resultant of the heating of the respectivedevices by resistors 25 and 26, and to the cooling of the devices by theflowing refrigerant. This refrigerant.

resultant temperature varies more widely than the temperatures alone ofthe refrigerant, and thus magnifies the response of 25 and 25'.

It will be noted that device 23' is disposed in a fitting in the outletpassage of the evaporator, although it may be placed in the suction pipenear the evaporator. Device 23 is located at a point in the latterportion of the evaporator at a point wherein the fiowing refrigerant mayinclude but never exceed a predetermined small percentage of liquidrefrigerant.

Condition responsive control devices 23 and 23' are similar, hence adescription of one should suifice for both. As schematically shown inFigure 1, and more fully shown in Figures 2 and 3, device 23 comprisesessentially a temperature responsive resistor 25 and a heater resistor26 in heat exchange relation therewith. The devices may be used inconjunction with a suitable fitting having a suitably enlargedrefrigerant passage therethrough or may be inserted directly into anevaporator passage. Preferably, the passage or fitting which receivesthe device or devices should have its walls so shaped as to I encouragesmooth flow along the surfaces of the temperature responsive elements.Figure 2, taken on line 2-2 of Figure 1, shows a sectional elevation ofa preferred form of device 23 and its associated fitting. A plurality ofturns of wire having a high temperature coefllcient of resistance (highpercentage change in resistance per degree temperature change), such asnickel, are wound on a suitable core 24, said windings being denoted bynumeral 25. In heat exchange relation with windings 25, are a few turnsof suitable heater resistor wire, shown at 26.

The elements comprising core 24 and windings 25-26 may be inserted in aprotective metal cover 23. Preferably, to improve the thermalconductance of the assembled windings and the cover, the windings may beimpregnated and the air spaces filled with suitable electricalinsulating and impregnating material including resinlike substances.Cover 28 not only serves to protect the windings but may also be used toattach the assembled element to cap portion 21, as shown in Figure 2.Cap portion 2'! acts as a cover or closure for the enlarged and openportion of evaporator 6, or a suitable fitting, and locates theassembled elements including the aforesaid windings in the path of theflowing refrigerant. Cap 21 may be of any suitable substance, includingresins, resin-like material, vitreous material, or the like. Wire 29extending through cap 21 is a lead from winding 25 but obviously anysuitable terminal means may be provided in said cap for windings 25 and26.

Figure 3, taken on line 3-3 of Figure 2, shows a horizontal section ofdevice 23 and its associated fitting. It is noted that the portion ofthe device located in the refrigerant passage has a substantiallystreamlined shape. This shape is chosen to insure relatively uniformconditions of heat transfer, it being considered that the variousdegrees of turbulence in a turbulence flow condition would nonuniformlyaffect the heat transfer from said device 23 to the flowing It is alsodesirable that the walls of the passage be suitably modified toencourage smooth and non-turbulent flow.

Although device 23 is shown as including a protective cover portion 28,it is contemplated that the winding element and cap 21 may be moldedtogether as a single unit, the windings being impregnated and protectedby the impervi- 6 ous molding material used. The molding material usedshould, of course, be impervious and resistant to the refrigerants used,resin or resinlike materials having good thermal conductivity and goodinsulating qualities being preferable. Also, the winding element may besuitably protected by molding material and then attached to the capportion in any desired manner.

While devices 23 and 23' are shown as extending transversely intofittings associated with an evaporator passage, it is also apparent thatthese devices may be differently shaped and located. For instance,either of the devices may be located near a bend portion of theevaporator and may comprise elongated elements extending longitudinallyof an evaporator passage.

With the control system arranged as described, it is apparent that thesystem will tend to operate at full capacity. It is sometimes desirable,however, to operate at less than full capacity to minimize short cyclingof the compressing equipment. For this purpose, and also to improve thetemperature regulation of the cooled medium, box temperature responsivedevice 30 is provided. Device 30 comprises a fluid chargedtemperatureresponsive bulb 3| connected by capillary tube 32 to bellows 33. Bellows33 operates to rotate pivoted arm 34, and thus move arm 36, associatedwith arm 34, across resistor 31. Spring 35 keeps arm 34 in contact withbellows 33 and may be used for adjustments. With relatively hightemperature at bulb 3|, bellows 33 is expanded, arm 36 is at maximumcounter-clockwise position, and device 30 adds no resistance to the lefthand branch of the control circuit. However, when the temperature atbulb 3| drops to a predetermined low figure, arm 36 is moved acrossresistor 31 and then adds resistance to said left hand control branch.Added resistance in this branch causes motor 2| to operate valve l5toward closed position and thus reduces the capacity of the evaporatorand prolongs the operating period of the compressor. Obviously, as theprimary control of the system is such as to operate same at the maximumsafe capacity, then the only feasible supplementary control is thatwhich reduces the capacity of the system.

When the refrigerating system is shut down, motor 2| will tend to drivevalve I5 wide open, in a manner which will later appear. This isgenerally not desirable for there is a tendency for the suction pressureto build up and a possibility that liquid refrigerant may enter thecompressor upon again starting. This is usually prer vented by providinga solenoid valve, or the like,

which closes when the system is shut down; however, by providing a shuntbetween the left hand control branch and a center wire 10, motor 2| canbe controlled to close valve i5. The shunt circuit is completed whenrelay I8 is deenergized, and broken when said relay is energized; hence,it causes motor 2| to close valve I5 whenever the system is shut down.

It is noted that the improved control means for a refrigerating systemhas been described in a rather specific manner. It should be kept inmind, however, that the present illustrations are given only to clearlydisclose the invention. Actually many changes and equivalents arecontemplated. While applicant prefers modulating electric motor means tocontrol his expansion valve. it is obvious that other reversible motorsbe used. Applicant finds electrical heating means more satisfactory, buthere again, any equivalent heating means is suitable. Because of thedesirably small temperature difference in the refrigerant at thelocation of devices 23 and 23', applicant prefers to add heat to hiscontrol devices toramplify their effect, as noted, but it is apparentthat other means may be provided to amplify the efiects of said controldevices. Further, by suitable compromises, a measure of control may beeffected without any amplifying means. In addition, heat may be added tocontrol devices 23 and 24 and then their controlling effect may beamplified by suitable means for controlling a motor.

To make the present disclosure more clear, the following operationportion of this specification will emphasize the function of theapparatus'just described. Further, to give concrete examples of some ofthe changes which may be incorporated in the present invention,modifications are described under Figures 4 and 5.

Operation of Figure 1 To make the description of the operation of thepresent control means more understandable,

certain assumptions may be made. The resistors 25 and 25' may each havearesistance value of 900 ohms at C.; resistor 22 may have a resistancevalue of 100 ohms, and the follow-up resistor of motor 2| may also havea resistance of 100 ohms. Resistor 64 has sufficient resistance to limitthe current flow in the shunt circuit to a safe value. The value of theresistor of control device 30 is not critical, and may depend on thedegree of control to be exercised by said device. The current regulatingcapacity of variable resistor 83 is such that heater resistors 25 and25' may be suillciently energized to heat devices 23 and 23' about 50higher than the ambient temperature in the evaporator when no fluid isflowing.

With the system shut down, due to manual switch l9 being opened, it maybe assumed that the head pressure and suction pressure are withinsuitable limits and the switching means of controller 20 is closed.Safety trap 38 is dry and switch 45 is closed. Relay I8 is deenergized;switch blade 40 is out of engagement with contact 4|, and switch blade42 is in engagement with contact 43.

Heater means 26 and 25' are energized and devices 23 and 23 are equal intemperature and about 50 warmer than the gaseous refrigerant in theevaporator. With equal temperatures of 23 and 23, resistors 25 and 25'have equal resistance values. 'It is now noted that the left hand branchof the control circuit, neglecting device 30, comprises resistor 25',whereas the right hand branch comprises resistor 25 and resistor 22.With resistors 25 and 25' of equal value, the right hand branch has 100ohms more resistance than the left branch. This unbalance actuates motor2| in a direction wherein it adds the 100 ohms of its follow upresistance to the left branch and thus balances the network. When themotor moves to add all of its follow-up resistance to the left branch,the valve is driven wide open, and when the motor runs in the oppositedirection, the valve is closed. With the system shut down as described,however, the shunt circuit comprising wire 56, contact 43, switch arm42, wire 53, resistor 64, and wire 65 extends between control wires 10and H and shunts one of the relay coils of the motor out of the circuit.The other relay coil, being the only one energized, causes the motor tobe driven in a direction to close valve I5 regardless of devices 23 and23.

- mediately acting to open valve I5.

Valve I5 is thus closed when the system is shut down. With the shuntcircuit causing valve 15 to be closed regardless of the devices 23 and23', it seems obvious that the temperature affecting bulb 3| has nocontrolling effect when the system is shut down.

With the condition of the system as Just outlined, closing manual switchIt! energizes relay I8 by the circuit: line 50, wire,5l wire 52, wire58, relay coil 44, wire 59, switch l9, wire 50, float switch 45, wire45, controller 20, wire 5|, wire 55, wire 56, and line 57. Energizingrelay l8 results in switch arm 42 being pulled out of engagement withcontact 43, and in switch arm 40 being pulled into engagement withcontact 4|. Opening the first named switch means removes the shunt fromthe control circuit of motor 2|, said motor im- Closing of the secondnamed switch of the relay causes the compressor motor to be energized,the circuit being: line 50, wire 5|, wire 52, contact 4|, arm 40, wire53, motor II, wire 54, wire 55, wire 55,

and line 51. The compressor I0 is thus started by motor ll.

With the system started, it is noted that the refrigerant flow throughevaporator It increases as valve [5 is opened. At the beginning of theoperation of the system, and before refrigerant starts to flow throughevaporator l5, devices 23 and 23 are at equal temperature and about 50warmer than the ambient temperature in the said refrigerant evaporator.As was previously noted, when devices 23 and 23' are equal intemperature, valve [5 tends to be driven wide open. The refrigerant flowwill thus tend to increase until the control circuit is altered in amanner to limit the valve movement.

Because of the residual heat of the evaporator and the small initialflow of refrigerant, the first refrigerant to circulate past devices 23and 23' is completely vaporized and therefore has rela-' tively littleeffect on said devices. Further, because of the comparatively low heattransfer ability of the vaporized refrigerant, the temperatures of thesaid devices are nearly equal.

As the evaporator picks up its cooling load and the refrigerant flowcontinues to increase, the temperatures of devices 23 and 23' will drop.However, so long as the flow passing both devices is gaseous, theirtemperatures will remain quite close together. For the purpose of thisillustration, it may be assumed that a maximum flow of gaseousrefrigerant will have sufllcient cooling effect on the devices 23 and23' to reduce the resultant temperature of said devices to about 35above that of said gaseous refrigerant, instead of the 50 differentialwhen there was no flow.

As the medium being cooled has its temperature reduced, and its heatingeffect on the evaporator is thus reduced, the liquid, or wetted surface,level of the refrigerant in the evaporator rises and advances toward theoutlet. As device 23 is upstream of 23', any change in quality of therefrigerant flow will affect device 23 first. When small amounts ofliquid refrigerant come in contact with 23, it not only tends to wet thesurface of said device, and thus increase the heat transfer rate, but italso absorbs heat to vaporize same. Small amounts of liquid refrigerantthus have much more effect in carrying away the heat of device 23 thandoes gaseous refrigerant. A relatively small amount of liquidrefrigerant will lower the temperature of 23 to that of said liquid.Assume that a refrigerant flow of 97% quality, that is, a flow wherein3% of the refrigerant is liquid and 97% is gaseous, will lower thetemperature of 23 to the vaporizing temperature of the liquid. It thenappears that a change in the quality of the refrigerant flowing acrossthe device 23 varying from 100% gaseous to 97% gaseous and 3% liquidwill cause a temperature drop of said device of 35.

The large temperature change at device 23 occasioned by a small amountof liquid refrigerant in the flow at said device causes aproportionately large variation in the ohmage resistance of temperatureresponsive resistor 23. Temperature of refrigerant having a smallportion of same in the liquid state is the vaporizing temperature ofsaid refrigerant and, at constant pressure, this temperature will remainthe same until all of the liquid is vaporized. Devices 23 and 23' are solocated and adjusted that a refrigerant flow including sufilcient liquidrefrigerant at device 23 to lower its temperature to the vaporizingtemperature of the refrigerant will gain a small amount, say 5, ofsuperheat by the time it reaches 23'. Should the quality of the flowvary to provide all gaseous refrigerant at vaporizing temperature atdevice 23, the superheat at 23' will tend to rise, but that rise will beslight, say 2, due to the low-rate of heat transfer to said gas.

It is noted above that a change in refrigerant flow which will cause asmall change in the superheat of the outgoing refrigerant, will cause achange of 35 in the temperature of control device 23 relative to 23.There is thus provided a considerably multiplied temperature responsewhich makes possible a highly accurate and responsive control means forregulating a control device. In addition, due to the small rate ofchange in the temperature coemcient of resistance of the nickel wireused for resistors 23 and 25', the precision of the control remainssubstantiallyconstant over a wide range of operating temperatures.

With sufllcient liquid refrigerant contacting device 23 to reduce itstemperature to that of said liquid, said temperature being about 35lower than that of device 23', the resistance of resistor 25 becomesabout 200 ohms less than that of 25'. If valve l5 was wide open, it wasnoted that the follow-up resistor of motor 2| was added to the left handcontrol branch of the control circuit, said follow-up resistor balancingout, resistor 22. If the right hand control branch now has itsresistancevaried to 200 ohms less than that of said left hand branch,motor 2| operates to add said follow-up resistance to the right handbranch and removes same from the left hand branch. With resistor 26having 200 ohms less resistance than 25', it is seen that it requiresthat both resistor 22 and the follow-up resistor of motor 2|, each of100 ohms resistance, be added to resistor 23 to balance the circuit. Itwas previously noted that valve I! was wide open when all the followupresistance was added to the left hand control branch; hence, with themotor having operated to its other extreme to add its follow-upresistance to the right hand branch. the valve is now driven closed.

With the system running, it is now clear that valve i5 is driven towardwide open position when only gaseous refrigerant flows past devices 23and 23', and the said valve isdriven closed when 3% of the flowingrefrigerant at device 23 is liquid. Thus a 200 ohm difference in theresistance value of resistors 23 and 23' is sumcient' to cause motor 2|to operate from one extreme to the other. Obviously, if the flowingrefrigerant at device 23 must have 3% of same in the liquid state todecrease the temperature of 23 35 5 below that of 23' and to cause a 200ohm unbalance in the control circuit, then a smaller quan-- tity orpercentage of liquid refrigerant will cause a lesser temperature dropandtherefore cause less unbalance inthe control circuit. Motor 2| willthen tend to assume an intermediate position and the flow will be socontrolled by valve I6 that the refrigerant flowing past 23 will containsome liquid refrigerant but not more than 3% of same.

Following the present description, it should be kept in mind that thevalues given are illustratlve only. Further, by changing the amount ofheat supplied to devices 23 and 23', device 23 may be made to respond toa larger or smaller percentage of liquid refrigerant. With the presentcircuit, it is noted that there is a small amount of heat generated inwinding 25 and 25' due to the control current flowing through same, butthis merely reduces the heat that must be supplied by 26 and 26'. Undersome circumstances, however, it may be possible to use large enough acontrol current to provide the requisite heating effect. Of course,theheat exchange properties of the devices 23 and 23' may also bealtered by design and construction changes, and thus become inherentlymore or less responsive to quality changes of the refrigerant.

S far. in this description of operation, it has been assumed thatmaximum capacity operation is desired of evaporator l8. However, if theevaporator has a light cooling load, the controller 20, or other suchcontrol means may cause frequent but short running cycles of thecompressor. To

minimize this short cycling, box temperature responsive device 36 isprovided in the left hand control branch of motor 2|. As before noted,device 30 comprises a variable resistor operated by temperatureresponsive bulb and bellows means. With temperature high at bulb 3|,bellows 33 is expanded and arm 36 is at the minimum resistance portionof resistor 31. The control circuit of motor 2| is thus not afiected bydevice 30 when temperatures affecting said de- 50 vice are relativelyhigh, or when said device is unsatisfied. However, when device 30becomes satisfied. bellows 33 is retracted, arm 36 moves across resistor31, and resistance is added to the left hand control branch of motor 2|.55 Adding resistance to the left hand branch affects the control circuitin the same manner as lowering the resistance in the right hand branch.Thus motor 2| is caused to move in a direction to add follow-upresistance to the right hand 00 branch, this direction of operationcausing closing movement of valve l6, before noted. A partial closing ofvalve l reduces the evaporator capacity, prolongs the operating period,and thus minimizes short cycling.

when the system is shut. down, as by manual switch l6 or by other means,the immediate result is an increase in suction pressure and a reducedrate of flow through the evaporator. This reduced rate of flow may causethe liquid 79 level to retract or retreat somewhat and thus cause device23 as well as 23' to be contacted only by gaseous refrigerant. As beforenoted, when these devices are equal in temperature, valve I6 is drivenwide open. Driving valve I3 7 open with the system shut down would causerefrigerant to boil out of condenser and receiver I3 and to distributeitself through the system, evaporator I6 being filled with liquidrefrigerant because of its being the coldest part of the system. Withthe equalized pressures throughout the system, and with the evaporator Ifull of liquid, starting the compressor might be hazardous.

To avoid the troubles associated with leaving valve I5 open when thesystem is shut down, motor 2I is controlled by the previously mentionedshunt circuit to drive valve I5 closed upon system shut-down. When therelay circuit is deenergized to cause said shut-down, arm 42 engagecontact 43 and one of the relay coils of motor 2| is shunted out of thecontrol circuit by the following circuit: wire 10, wire 68, contact 43,arm 42, wire 63, resistor 54, wire 55, and wire 1I. It is thus seen thatthe relay coil of the left hand branch is shunted out, hence the relaycoil of the right hand branch is the only one energized and, acting inthe same manner as though there is lower resistance in the right handbranch, it causes said motor to drive valve I5 completely closed.

In brief review, it is noted that a refrigeration system may becontrolled by operating the expansion valve with a modulating motor,said modulating motor being controlled by devices responsive to the heatexchange properties of the refrigerant at two spaced locationsassociated with the outlet portion of the evaporator. By usingtemperature responsive resistors at said locations, and using saidresistors directly in the control circuit of said motor, the resultingsystem is made desirably simple. Heat is added to the control devices sothat the actual temperatures to which said resistors respond are theresultant temperatures due to said heating and to cooling byrefrigerant. Because these resultant temperatures vary widely with smallchanges in liquid content of the refrigerant, the present controlapparatus is many times more responsive to changes in the refrigerantflow than are the known control systems of the prior art. Temperatureresponsive resistors, which interpret these changes in resultanttemperature in terms of electrical resistance, have relatively stableand dependable characteristics, hence the apparatus may be used withoutadjustment or change over a wide range of temperature. Further, it isshown that, by simple modifications of the apparatus, other controlfactors, such as box temperature, may be considered. It has beenpreviously mentioned'that the present examples are to be consideredillustrative only and not in a limiting sense. Various substitutions andalterations are obviously feasible in the present apparatus, such asdevice 30 being humidity instead of temperature responsive. Motor 2I mayhave a separate follow-up means, or in some instances, may be areversible motor floating between end positions. The effect of changingrefrigerant conditions is shown to be amplified by the addition of heatto the control devices, but it appears that the response to thedescription of the apparatus of Figure 4, which follows.

Figure 4 The system and apparatus shown in Figure 4 will be noted as amodification of Figures 13, and wherein temperature responsive resistorsare used to detect refrigerant temperatures at spaced locations.However, this modification differs from Figure 1 by providing adifferent electrical network circuit incorporating the resistors, and bymagnifying the controlling signal potentials from said network byclamp-needle amplifying means. The comparison of this modification withFigure 1 will become more clear as the description proceeds.

The basic refrigeration system used herein is the same as that of Figurel, and like parts have been given the same numerals. It is noted thatcompressor I0, driven by motor II, discharges through pipe I2 intocondenser and receiver I3. Receiver and condenser I3 discharges liquidrefrigerant through pipe I4 to an expansion valve I5 which controls flowthrough evaporator I6. Suction means I1 extends between the outlet ofevaporator I6 and the inlet of compressor I0.

The operation of the compressor may be controlled by controller 20,which responds to high pressure, suction pressure, and possibly boxtemperature, as before, and a manual switch I9. The circuit controllingmotor II is: line 50, wire 5I, manual switch I9, wire 52, controller 20,wire 53, wire 54, motor II, wire 55, and line 51.

Obviously, any suitable means of controlling the of the control devicesmay be amplified by other 7 means. In addition, other means thantemperature responsive resistors may be used to respond to the resultanttemperatures as herein described.

These and other changes and modifications are believed within the scopeof the present invention. To more fully consider possible modificationsof the present apparatus, reference is made operation of motor I I maybe used.

In this apparatus, as before, novelty is believed to lie in the meanscontrolling the expansion valve, the valve itself being conventional.The reciprocable stem of the expansion valve I 5 carries a rack IOIwhich is reciprocated by pinion I02. Rack I 0| carries a slider I25which coacts with follow-up resistor I23 in a manner to be described.Pinion I02 is driven through a gear train by a reversible motor I03,said motor I03 being controlled and operated by current supplied througha sensitive clamp-needle type relay I04. The motor I03 has a pair offield windings I83 and I88 and its direction of operation depends onwhich, if any, of the windings is energized by said relay. Relay meansI04, as herein used, is preferably of the sort shown in Gille et a1.Patent 2,331,183, issued October 5, 1943. "Upon reference to saidpatent, it will be noted that the sensitive element of this relay meanscomprises a galvanometer which responds to the unbalance of the presentelectrical network.

Essentially, and as schematically shown in Figure 4, relay I04 includescontrol input terminals I13 and I14 which are connected to and energizegalvanometer I80. Relay I04 also includes control output terminals I11,I18, and I10, and power input terminals I15 and I16. Galvanometer Iactuates switch arm I which is connected to power input terminal I16 andwhich may engage eitherof contacts I92 or I03, connected to outputterminals I11 and I19, respectively. Power input terminal I15 isconnected directly to control output terminal I18. Power is supplied torelay I04 by wire I84 from line 50 to terminal I16, and by wire I85 fromline 51 to terminal I15.

Box temperature responsive device I3I includes a fluid charged ,bulb I32connected by a capillary tube I33 to bellows I34. Bellows I34 causesmotion of pivoted arm I35 which sweeps over accuse resistor I06. In anunsatisfied condition, bellows I34 of device I3I is expanded and arm I36is at a position of minimum resistance on resistor I36. Upon reaching apredetermined low temperature at bulb I32, bellows I34 is retracted andarm I36 slides along resistor I36.

Temperature responsive devices I42 and I60 may be generally similar todevices 23 and 24 of Figure 1, with the heaters omitted. Resistors I43and I46 of devices I42 and I60, respectively, are preferably of wirehaving a high and relatively unchanging coeflicient of resistance, suchas nickel. If desired, the devices 23 and 23' of Figure 1 may be used,heating windings 26 and 26' not being used. However, because the heatexchange between said devices I42 and I50 and the flowing refrigerant isof less consequence than in the preceding example, the shape of thesedevices is not as critical as in said preceding example. These devicesmay be incorporated in suitable fittings, or inserted directly intoevaporator passages, as shown.

These control devices are associated together in the electrical networkherein used which is seen to be a modified bridge circuit and isgenerally designated by the numeral I I0. The source of current for. thecontrol network comprises battery I I I, one terminalof said batteryconnecting through wire II2 to input terminal H3, and the other terminalof the battery connecting through wire H4 to input terminal II 6. Theupper left hand branch of network IIO includes, in series, wire II6,resistance II1, wire II8, and output terminal H9. The upper right handbranch of said network includes, in series, wire I20, fixed resistanceI2I, wire I22, terminal I23, the portion of resistor I24 betweenterminal I23 and slider I26, and slider I25, said slider I26 beingconnected to the other network output terminal I26 by wire I21.

The lower left branch of network I I0 includes, in series from terminalII6, wire I30, box temperature responsive device I3I, wire I,temperature responsive resistor I43of device I42, wire I44, balancingresistor I46, and output terminal II9.

The lower right hand branch of said network includes, in series fromterminal II6, wire I48, temperature responsive resistor I46 of deviceI60, wire I5I, terminal I62, the portion of resistor I24 lying betweenterminal I62 and slider I26, and slider I25, said slider I26 beingconnected by wire I21 to the output terminal I26 of said network.Network output terminal H6 is connected by wire I6I to terminal I13, andterminal I26 connects by wire I02 to terminal I14. Thus an unbalance innetwork H0 is communicated to galvanometer I30 of relay I04, whichcontrols the operation of motor I03 in a manner previously related.

Because this system, as just outlined and as will be more fullyexplained later, will inherently drive motor I03 to close valve I5 uponstopping the operation of compressor I0, thermal time delay relay meansI60 is used to condition the control circuit in such manner that valveI6 will assume an open position during times of non-operation. Solenoidvalve I10, connected in parallel with heater I6I by wires HI and I12, isused to stop refrigerant flow to valve I6 when the system is notoperating, for reasons which will appear.

Relay I00 comprises a bimetal strip I66 carrying a contact which engagesa stationary contact when strip I66 is cool. when strip I66 is warmed byheater I6I, said strip warps and breaks the circuit through thecontacts. The heater is so designed relative to strip I66 so as torequire energization for a predetermined time before its heat issufficient to warp said strip. Heater I6I is energized by the circuit:line 60, wire 6|, manual switch I6, wire 62, controller 20, wire 63,wire I64, heater I6I, wire I63, wire I62 and line 61. Heater I6I is thusenergized in parallel with motor II. The contacts of relay I control ashunt comprising wires I and I 96, connected to wires I H and I44respectively. This shunt short circuits resistor I43, thus theresistance of the lower right hand branch of the net work is highcompared to the lower left branch. This unbalance, as before described,causes valve I6 to be opened. I

It should be noted in a description of the present system that many ofthe present devices are illustrative only and may be of different sortwithout essentially altering the system. For instance, I3I may just aswell be a humidity responsive apparatus, or the like, and device I60 maybe any suitable sort of time delay relay. Further, other conventionalamplifying means suitable for controlling the operation of a reversiblemotor in responseto the unbalance of a network circuit may be used, suchas an electronic amplifier. In addition, certain rearrangements in thecontrol network are considered feasible and within the bounds of thisinvention.

The relation and function of the apparatus in the present system will bemore fully explained in the following operation schedule.

Operation of Figure 4 With the parts in the positions shown, the

system is in normal operation and compressor I0 is being operated bymotor II. Motor II is energized by the circuit above described andsolenoid valve I10 and heater I6I of relay I60 are also energized inparallel with motor II, as previously set forth.

Valve I6 is shown as being about half open and, as device I3I is in anunsatisfied condition, control over motor I03, which operates valve I5,is being exercised only by temperature responsive devices I42 and I60.It is noted that temperature responsive device I42 is located far enoughupstream in the evaporator so that it may always be in contact withliquid refrigerant and thus be at the temperature of the liquidrefrigerant. Device I60 is located near the outlet of the evaporator,and it is intended that all refrigerant passing same must have apredetermined number of degrees superheat. Assuming that the refrigerantpassing device I50 should have at-least 4 of superheat, and not over 8of superheat, neglecting the effect of the box temperature responsivedevice, then it is seen that a change in relative temperature betweendevice I42 and device I50 of 4 should sufficiently unbalance saidnetwork IIII to cause valve [I6 to assume either of its extremepositions. For instance, when the superheat falls to 4, valve I5 shouldbe driven to its closed position to insure against liquid refrigerantleaving the evaporator. When the superheat rises to 8, valve I6 is fullyopen to permit full capacity operation of evaporator I6.

With the system in operating equilibrium, and the refrigerant flowingpast temperature responsive device I60 having about 6 of superheat,device I42 is at the vaporizing temperature of the refrigerant, andnetwork H0 is balanced in the following manner: the ratio of theresistance of the upper left hand branch of the network to that of thelower left hand branch of the network is the same as the ratio of theresistance of the upper right hand branch to that of the lower righthand branch of said network. With the network balanced as described,there is no output current at terminals H9 and I26, galvanometer I80 ofrelay I04 is not energized, and the system continues to operate asbefore.

Should the number of degrees of superheat of the refrigerant pass indevice I50 rise above 6, the resistance of temperature responsiveresistor I49 is increased and unbalances network IIO. This causescurrent to flow from network output terminals H9 and I26 to controlinput terminals I13 and I 14 of relay device I04 through wires I8I andI82, respectively. The flow of current to said input terminal energizesgalvanometer I80 and causes same to deflect to the right. Whengalvanometer switch arm I85 engages contact I 93, winding I83 of motorI03 is energized. Motor I 03 then rotates pinion I 02 in a direction toopen valve I5. The energizing circuit for said winding is: power inputterminal I16, galvanometer arm I85, contact I93, control terminal I19,wire I86, winding I83, wire I81, control terminal I18 and power inputterminal I15. Of course, it should be noted that the circuit withinrelay means I04 is only schematic and may not represent the actualcircuit within same.

It is noted, however, that as valve I5 is opened, slider I 25 is raisedalong resistor I 24 and thus decreases the amount of resistor I24 whichis in the network branch which contains temperature responsive resistorI49. The decrease in resistance of the upper portion of resistor I24tends to offset the increase in resistance of I49 due to the addedsuperheat. Further, the resistance of the lower portion of I24 isincreased, thereby increasing the resistance of the upper right-handbranch of the network. Thus the network is brought back into balance ata more widely open position of valve I5. The more widely opened valvemay supply suilicient refrigerant to decrease the number of degreessuperheat at device I50 to the previous six degrees. but if thesuperheat continues to rise, the network becomes unbalanced again, andagain rebalances at a more widely open position of the valve. When thesuperheat rises to 8, the valve will be fully opened. as before noted.

Should the number of degrees of superheat at device I50 diminish below aprevious level and under 8", network H0 is unbalanced in the oppositedirection. The current flow at output terminals H9 and I26 is in reversedirection and galvanometer arm I85 deflects to the left and engagescontact I92, thus energizing winding I08 01' motor I03 in a mannerpreviously described. This causes a reverse operation of motor I03 and aclosing motion oi said valve. As the valve is operated, slider I25 movesover resistor I24 to rebalance the network. Should the superheatcontinue to diminish, the valve will be further operated to reduce theflow, and when the superheat diminishes to 4, the valve will becompletely closed.

In the above discussion, box temperature responsive device I3I has beenignored. So long as the temperature affecting bulb I32 is relativelyhigh, and bellows I34 is expanded, arm I35 is at a position of minimumresistance on resistor I36 and the device has no effect on the network.However, as the temperature of the cooled medium is reduced, and bellowsI 24 is retracted thereby, arm I35 moves along resistor I36 and addsresistance to the lower left branch of the network. Added resistance inthe lower left branch has the same effect on the network as lessresistance in the lower right-hand branch and thus causes a closing ofthe valve and requiring a higher number of degrees of superheat atdevice I50 to rebalance the network. The reduction of capacity caused bydevice I3I tends to minimize short cycling and also permits closertemperature control even though the compressor be started and stopped inresponse to box temperature. When the evaporator is stopped with anevaporator full of liquid, appreciable cooling of a medium can takeplace after the compressor has stopped. This is minimized by increasingthe number of degrees of superheat as the medium cooling becomessatisfied.

Just as device I3I can cause the control system to maintain variousdegrees of superheat, so can variable resistor I45 vary the degrees ofsuperheat to be maintained. Variable resistor I45, in the lower leftbranch of the network H0, is used to adjust the network to maintain adesired superheat.

Assume now that the system is shut down due to controller 20, or theopening of manual switch I9. Upon stopping the system, it is noted thatthe circuit supplying current to heater I6I and solenoid valve I10 isdeenergized. Solenoid valve I10 immediately closes and prevents furtherflow of refrigerant to the evaporator. The time delay relay cools andcloses its contacts. Closing the contacts of relay I60 causes resistorI43 to be shorted out of the network circuit by wires I and I96, whichconnect to wires MI and I44, respectively. Whatever the position ofvalve I5 when the compressor was stopped, the closing of solenoid valveI 10 stops all further refrigerant flow to the evaporator, and becauseof the lack of flow through evaporator I6, devices I42 and I 50 assumeequal temperature. This equal temperature due to shut down has the sameeffect on the network circuit as lowering the superheat to zero,therefore the circuit would normally control the operation of motor I03to drive valve I5 closed.

There is no harm in valve I5 being closed when the system is shut downbut, with the valve closed, the refrigerant flow cannot be establishedagain on starting the compressor. However. by shunting resistor I43 outof the network I I0. as above described, motor I03 is caused to operatein a manner to open valve I5. Thus, when the solenoid valve is opened,refrigerant flow may be established. Control devices I42 and I50 thencome within the influence of said flow before the thermal time delayrelay opens its contacts and removes the shunt. As was previously noted,when the resistance of the lower right-hand branch of the controlnetwork is relatively high, the valve is opened. In this case, theresistance of the lower right-hand branch has been made relatively highby lowering that of the lower left-hand branch. The period of timerequired to open the contact of time delay relay I60 is so chosen as topermit a suflicient refrigerant flow to be established so that devicesI42 and I50 can take over the control of valve I5 in the intendedmanner.

In review, the expansion valve of the present refrigerating system isoperated by a reversible electric motor. The motor is controlled tooperate for a period of time and in a direction determined by anelectrical network associated with sensitive relay means. The networkcomprises spaced temperature responsive resistor means located so thatone is kept at the vaporizing temperature of the refrigerant, whereasthe other responds to the superheated outlet gas temperature. A rise intemperature at the outlet relative to the vaporizing temperature,unbalances the network to cause the valve to be opened. whereas adecrease in the outlet temperature, relative to the vaporizingtemperature, causes said valve to be closed. Supplementarycontrolfactors may be considered in the network by varying the resistance of abranch of the network. Further, to insure the valve being opened at thestart of operation of the system, a portion of the network is modifiedby a shunt controlled by a time delay relay, the relay being energizedby the circuit controlling the compressor operation.

It is noted that certain modifications are obviously within the scope ofthe present invention. For instance, relay I may be of any suitablesort, or may be more in the nature of amplifying means, such as anelectronic amplifier. The time delay relay may be of any suitable sort.In addition, the particular part of the network modified by the actionof said time delay relay device is subject to certain changes. The boxtemperature responsive device 3| may or may not be used and it, too, maymodify the network in a manner other than shown, if desired. These andother changes will be readily apparent to those skilled in this art.

In this modification, as in the preferred extem is illustrative only andis subject to wide variation.

ample, control means are disclosed which regulate the action of a motoroperated expansion valve in response to the temperature differentialbetween spaced devices associated with the re-. frigerant fiow throughthe evaporator. As both devices respond to temperature, their responsesto changing conditions are uniform and equally rapid. The temperatureresponsive resistors used have a relatively stable temperaturecoeflicient of resistance and thereby make the control system accurateand efficient over a wide range of operating conditions. It is notedthat. due to the improved control means described, the present systemsare quickly responsive, accurate and dependable at any operatingcondition within a wide range. These characteristics make possibleanother advantage; namely, the control of the system to a relativelysmall number degrees of superheat, thus increasing the efiectiveness ofthe system for its intended purpose. These and other advantages arebelieved inherent in greater or lesser degree to both of the examplesgiven. Another modification incorporating many of the advantages recitedand having other advantages peculiar to itself will be found describedunder Figure 5, which follows:

Figure 5 The system of Figurej is quite similar to that of Figure 1, butdiffers therefrom in using fluid temperature responsive means forcontrolling the operation of the expansion valve rather than electricalmeans as in Figure l. The basic While the expansion valve used atpresent is shown to be different from that of the other figures, it maybe the same as valve l5 and have its fiuid motor as a separate unit.However, itis quite conventional to combine a fluid motor with anexpansion valve and this has been done in this instance. Expansion valve2| 5, which controls the refrigerant flow from pipe I to evaporator IO,comprises movable valve member 2l6 which is connected to flexiblediaphragm 2l'i. Diaphragm 2| I separates the motor portion of said valve2|! i'nto compartments M8 and M9. Obviously, differences in pressurebetween chambers 2|! and 2| 9 will tend to cause movement of saiddiaphragm 2H and associated valve member Ill. Valve member 2|6 anddiaphragm 2|! are constantly urged upwardly, or toward a closedposition, by spring 220. is connected to suction pipe ll of therefrigeratlng system by tube Hi and pipe 222, whereas chamber 2" isconnected to a closed receptacle.

225 by tube 228. In the structure recited, valve member 2i! is urgedtoward closed position by spring 220 and by pressure in chamber 2I9,corresponding to suction pressure, and is urged toward open position bythe pressure existing in chamber 2", corresponding to that in receptacle225.

Receptacle 22! is a closed vessel having an upper connection to tube228, as before noted, another upper connection through restrictor means221 to pipe 222, and a third connection to tube 228 which connects tothe outlet of pilot valve 280. The inlet of valve 230 is supplied withliquid refrigerant through tube 23] which is also connected to liquidrefrigerant line H. Tube 2" includes solenoid valve 2H), previouslymentioned. Valve 22!! comprises movable member 232 which controls flowfrom tube 23I to tube 222.

It will now be noted that the position of valve member 232 willdetermine the position of expansion valve member 2. The pressure inchamber 2|! always corresponds to suction pressure. The pressure inchamber 2! corresponds to that in receptacle 225, which depends on thecomparative rates of flow into and out of said receptacle. The fiow outis through restrictor 221, and flow in is through valve 230. If the flowthrough valve 220 is stopped, pressure in 225 will be reduced to-suctionpressure, and thus the pressure in chambers 2| 8 and H9 will be thesame. Valve member 2 I6 is then closed by spring 220. With pilot valve230 open, the pressure in 22! will exceed the suction pressure by anChamber 2 I 9' the flow through restrictor 221 is at varying pressuresand, without receptacle 225, both liquid and as may flow through same.Receptacle 225 is provided to insure that only gaseous refrigerant willflow through the restrictor 221, thus keeping its flow characteristicsuniform. If the ambient temperature at the location of said receptacleis not high enough to insure the vaporization of any liquid that may becollected in same, the receptacle may be placed in heat exchangerelation to a liquid line, the compressor cooling system, or the like.Further, rather than a separate re ceptacle, 225 may comprise an outerchamber associated with pilot valve 230, said outer chamber thus beingin heat exchange relation to the inner liquid chamber of said valve.

Valve member 232 of ilot valve 23!) is operated by a pivoted lever 234,which is connected by link 235 to pivoted lever 236 of differentialcontroller 240. Controller 24!] comprises oppositely arranged bellows241 and 25! operating against pivoted lever 23; in such manner that theposition of said lever is a resultant of the forces of the opposingbellows. Bellows 241 and 25! are driven by fluid pressure transmittedthrough capillary tubes 246 and 250, associated with devices 242 and244, respectively.

Devices 242 and 244 are similar and a description of one is pertinent tothe other. Device 242 comprises a fluid charged bulb 245 connected totube 246, and arranged longitudinally in a passage of evaporator !6. Aheater element 255 is arranged in heat exchange relation with said bulbfor a purpose which will be explained.

Device 244 is arranged in the outlet passage of evaporator !6, althoughit may be in the suction pipe near said evaporator. Device 242 ispositioned at a point beyond which the refrigerant flow should nevercontain more than a predetermined small quantity of liquid refrigerant.As in the first example, the present control devices and the surroundingrefrigerant passages should preferably be shaped to minimize turbulencein the refrigerant flow.

Heaters 255 and 256 of devices 242 and 244 are energized as follows:line 50, wire 210, rheostat 258, wire 21!, heater element 256, wire 212,heater element 255, wire 213, and line 51.

As is well known, the pressure exerted by a bulb-bellows arrangement isdependent on the temperature affecting the bulb. Thus the pressuresexerted by bellows 241 and 25! are dependent on the temperatures ofbulbs 245 and 249, respectively. Relatively high temperature at bulb 249will be seen to cause bellows 25! to force lever 236 counterclockwise,thus closing pilot valve 230 and resulting in closing of expansion valve2!5. Likewise, relatively high temperature of bulb 245 will result inexpansion valve 2!5 being opened.

In addition to bellows 241 and 25! acting on lever 236, a bellows 260,connected by capillary tube 26! to box temperature responsive bulb 262,is provided. Bellows 26D coacts with lever 236 through an arm 263 havingan angularly disposed pivot portion 264 bearing against the righthandside of said lever. Pivot portion 264 and lever 236 is spaced far enoughaway from bellows 260 that expansion of said bellows will have no effecton said lever. However, contraction of bellows 260 will cause pivotportion 264 to bear against and to move lever 236 counterclockwise. Thusa predetermined low temperature of bulb 262 will result in the expansionvalve 2!5 being adjusted toward closed position.

Although fluid operation of the expansion valve is illustrated, it isapparent that lever 236 might be used to operate a controlpotentiometer, or like means, associated with an electric motor foroperating expansion valve 2l5. This and other modifications of thepresent apparatus are believed obvious when considering the presentinvention as a whole.

To more fully disclose the function and cooperation of the various partsof the present control means, a fuller description of theoperation ofthe system of Figure 5 follows:

Operation of Figure 5 With the parts in the position shown, the systemis at rest, motor is not operating, solenoid valve 2 I0 is closed,expansion valve 2 !5 is closed, and pilot valve 230 is opened. Aspreviously noted, control devices 242 and 244 include temperatureresponsive bulb means 245 and 249, respectively. When refrigerant isflowing through the system, these bulbs respond to the resultanttemperatures due to the effect of refrigerant flowing past same and theheat being added by their heaters. But no refrigerant is flowing, thereis nothing to cause a temperature differential to exist between them andtheir effect on their respective bellows are equivalent.

It may be assumed that sufficient current is supplied to heater elements255 and 256 so that bulbs 245 and 249 will be about 50 warmer than theambient temperature in said evaporator when there is no flow throughsame.

Controller 240 and pilot valve 230 are initially adjusted so that acondition of zero temperature differential between devices 242 and 244will result in said valve 230 being wide open. As before noted, valve230 controls refrigerant flow from tube 23! to tube 228, but, assolenoid valve 2!!) in tube 23! is closed, there is no flow through saidpilot valve. In consequence, the pressure existing in receptacle 225 isdue to the communication of said receptacle through restrictor 221 andpipe 222 with suction means !1. However, the pressure in chamber 2!!) ofvalve 2!5 is also due to that existing in suction means I1. As thepressures existing in chambers 2!8 and 2!9 are equal and opposite, valvemember 2!6 is then driven closed by spring 220.

To place the system in operation, manual switch !9 may be closed and, ifthe switches in controller 20 are closed, relay coil 244 is energized bythe circuit: transformer secondary 206, wire 58, solenoid valve 2!0,wire 59, controller 20, wire 60, relay coil 44, wire 6!, switch !9, wire62, and said transformer secondary 206. Energization of relay coil 44pulls switch arm 40 into engagement with contact 4! and starts motor I!by the circuit: line 5!], wire 5!, wire 52, contact 4!, arm 40, wire 53,motor !I, wire 54, wire 55, and line 51. Compressor I0 is now operatingand compressing refrigerant which is liquified in condenser l3.

As before stated, however, valve 2l5 was closed hence no refrigerantflow from condenser and receiver !3 can immediately take place throughvalve 2!5. However, the opening of valve 2!!) permits high pressurerefrigerant to flow through tube 23! and open pilot valve 230 intoreceptacle 225 thereby raising the pressure within said receptacle. Atthe same time, operation of the compressor has started to reduce thesuction pressure in I1; hence with the lowering of the pressure inchamber 2!!! and an increasing of the pressure in chamber 218, the forceof spring 220 ward open position. Refrigerant flow through saidva'lve2i5' into evaporator" is thus graduallystarted. {While itmayappear that the head ressure ofathe system would tend to rise and open aswitch of controller 26, due to valve 2l5 being closed, it is noted thatthe head pressure is dependent on the condenser temperature, thecondenser, not having been used for some time, shouldbe sufficiently lowin temperature to keep said head pressure from rising. It is of course,assumed that the condenser and receiver II have adequate capacity tohold the liquifled refrigerant of the system.

With a flow of refrigerant now established in evaporator, I6 and withpilot valve 230 wide open, valve 215 is drivento a wide open positionhence evaporator l6 tends to be loaded to'its maximum capacity. 80 longas gaseous refrigerant only is flowing past bulbs 245 and 249, they dropbut little in temperature due to the relatively low heat transferabilities of the gaseous refrigerant, it being noted that heaters 255and 256 are energized by the circuit previously related. As bulbs 245and 249 are equally heated, and as they are both being swept across bygaseous refrigerant,

their temperature drop is relatively small and rather uniform becausethe temperature of the gaseous refrigerant is changed relatively slowlyas it passes through the evaporator. There is thus little temperaturedifl'erential to cause the operation of controller 246, therefore pilotvalve 2" remains open until liquid refrigerant comes in contact withbulb 245.

When liquid refrigerant begins to contact bulb 245, it removes heat fromsaid bulb at a much higher rate than the gaseous refrigerant due to itsbetter heat conductive properties and its ability to absorb heat tochange its state. A comparatively small amount of liquid refrigerantcontacting bulb 245 is sufficient to cause a marked lowering oftemperature of said bulb. As a. lower temperature of a fluid-chargedbulb causes a reduction in pressure of the fluid in said bulb, bellows241 is contracted and arm 236 of controller 246 is movedcounterclockwise by the higher pressure of bellows 25l, therebyactuating valve member 232 of pilot valve 230 toward closed position.

When pilot valve 230 was open, the pressure existing in receptacle 225was high due to high pressure refrigerant being supplied through tube23l, valve 230, and tube 228 at a higher rate than it could flow fromsaid receptacle through restrictor 221 to the suction line. However, asvalve 230 is moved toward closed position, the pressure in receptacle225 is lowered and, as said pressure is the resultant of the inward flowthrough the pilot valve and the outward flow through the restrictor, themore nearly valve 230 approaches closed position, the more nearly thepressure existing in chamber 225 approaches that of suction means ll. Asbefore noted, since chamber .2l9 always exists at suction pressure, thenas chamber 2 l 8 approaches suction pressure, spring 220 is able to urgevalve member 2i6 toward closed position, thus reducing the flow to theevaporator and permitting a larger portionof the refrigerant to vaporizebefore reaching bulb 245.

By adjusting the amount'of heat furnished said bulb, the percentage ofliquid required in the refrigerant flow passing bulb 245 to reduce thetemperature of the bulb to the vaporizing temperature of the refrigerantmay be varied.

2", is urged 1'0- As was previously stated, sufficient heat maybe addedto raise the temperature of the bulb about 50 above the ambienttemperature in the evaporator when there is no circulation. Then, assumethat with gaseous refrigerant only flowing, the temperature may bereduced about 15 at each of said bulbs. When a suillcient quantity ofliquid refrigerant contacts bulb 245, its temperature may drop to thatof the liquid refrigerant. When the temperature of bulb 245 drops toliquid temperature, and with bulb 249 reduced only about 15, thereresults a diflerential of about 35 for actuating controller 240. Theability to obtain a temperature differential of 35 from a variation inrefrigerant quality at the location of device 242 from gaseous to, forinstance, 97% gaseous'and 3% liquid, makes this a highly sensitivecontrol means.

Obviously device 242 may be located at such a position that liquidrefrigerant will always contact same, and control may be affected bydevice 244 on a basis of superheat, as in the example of Figure 4, butnote that to control on the basis of superheat, 35 of superheat must beobtained to give the same temperature difference to actuate device 240.Thirty-five degrees of superheat is normally considered excessive formaximum operation of a system and would not be acceptable in mostinstallations. By controlling on the basis of heat-dissipatingcharacteristics of the flowing refrigerant, the precision and speed ofresponse on the present apparatus makes it possible to more fullyutilize the evaporator than is feasible with conventional controlsystems. Thus a change in refrigerant quality in device 242 from 100% to97% is sufllcient to operate expansion valve 2l5 from'fully open toclosed position. When the refrigerant contacting bulb 245 contains 3%liquid, for instance, the bulb temperature is lowered to that of theliquid, bellows 241 is retracted and bellows 25l is able to push lever236 to its counterclockwise limit. As before described, this closespilot valve 230 and causes expansion valve 2l5 to close. As beforenoted, when'no liquid refrigerant is contacting bulb 245, itstemperature rises to approximately that of bulb 249. When 'both bulbsare at equal temperature, the expansion valve is drivenopen.

As in the previous instances, the present system is intended to operatethe evaporator at maximum capacity but, at times, it is desired toreduce the capacity of the evaporator to minimize short cycling, or forimproved temperature regulation. Upon a reduction in temperature at bulb262, the pressure imposed on bellows 260 is diminished and portion 264of link 263 is pulled against arm 236 and serves to rotate samecounterclockwise. This urges pilot valve 230 toward closed position andtends to close Valve 2l5, thereby reducing the capacity of the systemand lengthening the period of operation of the system.

valve 2|0 immediately closes. With the supply of high pressurerefrigerant to receptacle 225 thus cut off, the pressures in saidreceptacle and chamber 2l9 are quickly equalized. This permits spring220 to close valve member 2i6; hence, expansion valve 2 I 5 is closedduring periods of nonoperation of the'system.

In each of the examples herein given, means are provided to control anexpansion valve in response to temperatures at spaced locations in therefrigerant circuit. This results in uniform control conditions andmakes feasible higher load- Upon shut down of the system, the solenoidings of an evaporator than was previously con sidered safe. Due to theuse of temperature responsive resistors for control elements, theoperating characteristics of the system remain quite uniform over widelyvarying conditions of operation. Then, by supplying heat to temperatureresponsive means so that said means responds to the temperatureresulting from said heat and the cooling effects of the flowingrefrigerants, it is possible to gain a large response from small qualitydifferences in refrigerant fiow. Thus, the novel devices and systemsdisclosed in this application are believed to improve the art ofrefrigeration.

It is to be noted that many substitutions and equivalents have beenmentioned in the present disclosure, but these cannot represent all themodifications that will be obvious to one skilled in the art upon studyof this specification and drawing. Therefore, it is intended that theexamples given be considered as illustrative only and that the scope ofthe invention be determined only by the appended claims.

I claim as my invention:

1. In a refrigerating system, in combination, a condensing unit having aliquid refrigerant supply means and a gaseous refrigerant receivingmeans, an expansion valve, an evaporator, said valve being connected tosaid supply means for controlling refrigerant flow to said evaporator,reversible motor means for actuating said valve between open and closedpositions, and a normally balanced electrical network circuit means forcontrolling the operation of said motor means, said circuit meanscomprising a plurality of spaced electrical temperature responsiveimpedance means, one of same being located within and near the exit ofthe evaporator and another of said impedance means being located withinthe evaporator and upstream of said one electrical impedance means.

2. In a refrigerating system, in combination, a condensing unitcomprising a compressor, a motor driving said compressor, an expansionvalve, an evaporator, said unit supplying liquid refrigerant throughsaid expansion valve to said evaporator, the outlet of said evaporatorbeing connected to the inlet of said compressor, reversible motor meansoperatively connected to said valve for actuating same, electricalnetwork circuit means having a plurality of branches controlling theoperation of said motor, said circuit means comprising first and secondresistance means each having a relatively high temperature coefiicientof resistance and located in the path of the flowing refrigerant of thesystem, said first resistance means being located at a point past whichonly gaseous refrigerant should flow, said second resistance means beinglocated upstream of said first means at a point wherein the flowingrefrigerant should include a small portion of liquid, said firstresistance means being in one branch of said network circuit and saidsecond resistance means being in another branch of said circuit, meansresponsive to the'temperature of the medium being cooled for varying theimpedance in one of said branches, means supplying predetermined andrelatively uniform amount of heat to each of said resistance means, andmeans simultaneously actuated with stopping of the compressor motor forshort circuiting one of the branches of said circuit to cause saidreversible motor to drive said valve closed when the compressor isstopped.

3. Refrigerating apparatus comprising, in

combination, an evaporator, said evaporator having a passage throughwhich refrigerant may be circulated, and a temperature responsive devicelocated within said passage in a position to be contacted by refrigerantflowing through said passage, said device including heater meansarranged to be continuously and uniformly heated when said apparatus isbeing used.

4. Refrigerating control means comprising, in combination, a temperatureresponsive device suitable for insertion into a conduit carrying flowingrefrigerant, said device being shaped in a manner to cause a minimum ofturbulence of fluid flow, attachment means for securing said device in arefrigerant passage, heater means disposed within said device and inintimate thermal relation therewith, connection means for said deviceextending through said attachment means, and connection means for saidheater means also extending through said attachment means.

5. Refrigerating means, comprising, in combination, an evaporator, saidevaporator having a passage through same for circulation of refrigerant,and a plurality of control devices located within said passage in amanner to be contacted by said circulating refrigerant, one of saiddevices being located near the outlet of said evaporator and another ofsaid devices being located a predetermined distance from said one devicein a direction toward the inlet of said evaporator, said devices eachincluding electrical resistance means having a relatively hightemperature coefficient of resistance, at least said device toward saidinlet including a heater means.

6. In a refrigerating system having an expansion device and anevaporator, motor operated means for controlling a flow of refrigerantthrough said expansion device and evaporator, and a plurality oftemperature responsive devices operatively connected to said motor toreversibly control its operation, said temperature responsive devicesbeing spaced apart and located in the path of the refrigerant, saidtemperature responsive devices including means for heating them severaldegrees above an ambient of circulating gaseous refrigerant.

7. In a refrigerating system, a source of liquid refrigerant underpressure, an expansion valve, an evaporator, said valve being connectedto said source and said evaporator for controlling refrigerant flowthrough said evaporator, reversible motor means operatively connected tosaid valve for opening and closing same, electrical network circuitmeans, said circuit means including electrical resistance means havingan appreciable temperature coefficient of resistance associated withsaid evaporator at spaced points, one of said points being near theoutlet and the other of said points being upstream of said one point,means for adding substantially uniform quantities of heat to each ofsaid resistance means, and amplifying means responsive to the unbalanceof said network circuit means, said amplifying means controlling saidmotor means in a manner to maintain a predetermined state of balance ofsaid network circuit means.

8. In a refrigerating system, a source of liquid refrigerant underpressure, an expansion valve, an evaporator, said valve being connectedto said source and said evaporator and arranged to regulate a flow ofrefrigerant through said evaporator, reversible motor means foroperating said valve between minimum and maximum flow positions, and a,control circuit means for said motor, said circuit means including aplurality of temperature responsive elements located at spaced points inthe path of flow of said refrigerant, means for adding predeterminedquantities of heat to each of said elements so that said elements mayrespond to the heat exchange properties of said re- ;frigerant at saidelements, said control circuit being connected and adJusted to causestable refrigerant flow conditions when the heat exchangecharacteristics of refrigerant at one of said elements differs from thatat another of said elements, a change in said characteristics at saidone of said elements which is not reflected in a like change at saidother element causing opera? tion of said motor to restore the previousrelation of characteristics between said points.

9. In a flow control system, in combination, a valve, reversible motormeans for actuating said valve, and control means for said motorcomprising a plurality of devices each including temperature responsivemeans and heater means, the temperature responsive means of each of saiddevices normally responding to the resultant temperature due to saidheater and the influence of the medium, such as a flowing fluid,surrounding said device, said devices being connected in controllingrelation to said motor in such manner that a change in resultanttemperature of one device relative to another causes operation of saidmotor and valve to permit a change in flow of a sort to restore theprevious relation of resultant temperatures.

10. In a refrigerating system comprising a I source of liquidrefrigerant under high pressure,

a supply of gaseous refrigerant under low pressure, an expansion valve,an evaporator, said ex-.

pansion valve being connected to said source and said evaporator andcontrolling refrigerant flow through said evaporator, the outlet of saidevaporator providing said supp y of gaseous refrigerant; control meansfor said system including a reversible motormeans for actuating saidvalve, a plurality of control devices each comprising temperatureresponsive means and heater means, said devices being locatedin the pathof the circulating refrigerant. one of said devices being located in aportion of the system beyond which no liquid refrigerant should pass,the other of said devices being located upstream of said one device in alocation where it will be contacted by liquid refrigerant, saidtemperature responsive means responding to resulting device temperaturesdue to the heating effect of the heater means and the cooling efiect ofrefrigerant contacting same, and control circuit means including poweramplifying means controlling said motor in response to said plurality ofcontrol devices, said devices exercising control over said amplifyingmeans and said amplifying means controlling said motor.

11. In a refrigerating system, in combination, a condensing unit havingan outlet supplying liquid refrigerant under pressure, said unitincluding suction means receiving gaseous refrigerant under lowerpressure, an expansion valve, an evaporator, said expansion valve beingconnected to said outlet and to said evaporator chambers, conduit meansconnecting the other of said chambers to said, suction means, andconduit means including a restriction connecting the upper portion ofsaid receptacle to said suction means, said expansion valve beingactuated in response to the relative rates of flow through said pilotvalve and said restriction.

12. In a refrigerating control apparatus, a pair of devices arranged tobe inserted in a stream of flowing refrigerant, one of said devicesbeing upstream of the other, each of said devices-including temperatureresponsive means and heater means, said temperature responsive meansresponding to the resultant temperature of said devices due to theinfluence of said refrigerant and said heaters, reversible motor meansfor actuating an expansion valve for controlling the rate of flow ofsaid stream, and means controlling the operation of said motor inresponse to said temperature responsive means.

13. In a control apparatus responsive to changes in heat absorbingability of a flowing fluid of changing quality, a movable member, acontrol device operable by said member, a pair of opposed force exertingbellows coacting with said member in such manner that said member ismoved in response to the resultant of the forces exerted by said:bellows, a pair of fluid-charged bulb means each connected by tubemeans to its respective bellows, and heater means in heat exchangerelation with at least one of said bulbs, said heater means beingarranged for continuous and uniform energization, said bulb means beingdisposable at spaced locations in the path of said flowing fluid.

14. Refrigerating control means comprising, in combination, anelectrical resistor means having an appreciable temperature coeflicientof resistance, an electrical heater means in heat exchange relation withsaid resistor, means consolidating said resistor and heater in' aunitary element adapted to be inserted into a conduit carryingrefrigerant, said consolidating means being suitable to protect saidresistor and heater means from said refrigerant =but providing a goodthermal path between said resistor, heater means and said refrigerant,said resistor means being adapted to respond, when said heater isenergized, to the temperature of said element resulting from the effectsof said heater and said refrigerant.

15. -In a control apparatus responsive to changes in heat absorbingability of a flowing fluid of changing quality, a movable member, acontrol device operable by said member, a pair of opposed force exertingbellows coacting with said member in such manner that said member ismoved in response to the resultant of the forces exerted by saidbellows, a pair of fluid-charged bulb means each connected by tube meansto its respective bellows. heater means in heat exchange relation withat least one of said bulbs, said heater means being arranged forcontinuous and uniform energization, said bulb means being disposable atspaced locations in the path of said flowing fluid, and additional forceexerting condition responsive means arranged to move said member in onedirection in response to changes in said condition.

16. In a refrigerating control means, in combination, a conduit having arefrigerant passage therethrough, and a temperature responsive deviceincluding heater means disposed in said passage, said device having astreamlined shape, said passage surrounding said device being shaped tocooperate with the streamlined shape of said device to maintain smoothflow conditions under varying rates of fluid flow.

1'7. A refrigerating control device comprising, in combination, anelectrical resistor having an appreciable temperature coefficient ofresistance, an electric heater element closely associated with saidresistor, a container of streamlined shape receiving said resistor andsaid element, means consolidating said resistor, element and containerin a manner to provide good heat transfer characteristics for saidassembly, and a cover in sealing relation over said container throughwhich extends leads to said resistor and said element.

18. In a refrigerating system, in combination, a condensing unit havinga liquid refrigerant supply means and a gaseous refrigerant receivingmeans, an evapora r connected to said supply means and to said receivingmeans, a valve for controlling the flow of refrigerant through saidsupply means, motor means for actuating said valve between open andclosed positions, an electrical network circuit for controlling theoperation of said motor means, said circuit including a plurality ofspaced temperature responsive electrical impedance devices, one of saidimpedance devices being located in a manner to contact refrigerant nearthe exit of the evaporator and another of said impedance devices beinglocated upstream of said one impedance device in a manner to contact therefrigerant at said upstream location, and means for continuously anduniformly heating one of said impedance devices by a predeterminedamount.

19. In a refrigerating system including a compressor, a condenser, anadjustable expansion valve and an evaporator, said expansion valve beingarranged to control refrigerant flow from said condenser to saidevaporator, suction means connecting the outlet of said evaporator tothe inlet of said compressor, condition responsive control means foradjusting the expansion valve in a manner to maintain maximum quantitiesof liquid refrigerant in said evaporator, motor means for operating saidcompressor, safety trap means including a float operated switch connected to said suction means, and electric circuit means for controllingthe operation of said motor means, said circuit means including saidfloat operated switch whereby the presence of liquid refrigerant in saidsafety trap means will cause said float operated switch to open itscontacts and stop the motor means, thus protecting the compressor fromdamage.

LAMONT B. KOONTZ.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS

